Proportional valve, in particular for a camshaft adjuster

ABSTRACT

A proportional valve ( 1 ), including a piston guide sleeve ( 4 ) and a valve piston ( 3 ) that can be moved in the piston guide sleeve ( 4 ), and further including a check valve ( 13 ) arranged in a pressure medium inlet ( 10 ) to the proportional valve ( 1 ). According to the invention a proportional valve ( 1 ) is provided, in which the adaption of the check valve ( 13 ) to the proportional valve ( 1 ) is improved with respect to the prior art. This is achieved in that the check valve ( 13 ) is arranged in an annular gap ( 14 ) surrounding the piston guide sleeve ( 4 ) in a region of the pressure medium inlet ( 10 ).

FIELD OF THE INVENTION

The invention relates to a proportional valve with a piston guide sleeve, a valve piston that can move in the piston guide sleeve, and also a check valve arranged in a pressure medium inlet to the proportional valve. The invention also relates to an installation method for such a proportional valve.

BACKGROUND

Such a proportional valve is known from DE 10 2005 060 111 A1. This proportional valve is designed for a camshaft adjuster for an internal combustion engine and is integrated into a central screw for attaching the camshaft adjuster to a camshaft. Here, the proportional valve has a check valve that has a spring disk-shaped construction and is arranged in an annular pressure medium inlet laterally next to the proportional valve on the outer periphery of the central screw. During installation, care must be taken that this check valve arranged separate to the proportional valve is installed and there is also the risk of damage at least when screwing the central screw holding the proportional valve into the camshaft.

Another check valve is known from EP 1 291 563 A2. This check valve is designed for and integrated in a proportional valve constructed especially as a cartridge valve. Here, this check valve is inserted in the area of a pressure medium inlet into a recess provided on the inner periphery of the piston guide sleeve before installation of the valve piston. Here, the installation costs of such a check valve inserted into the piston guide sleeve are considerable. In addition, the stroke of this check valve constructed as a spring ring is not limited inwardly and the spring ring consequently can collide with the valve piston. Such a collision can lead to failure of the proportional valve.

SUMMARY

The invention is based on the objective of offering a proportional valve, in particular for a camshaft adjuster of an internal combustion engine, wherein the adaptation of the check valve to the proportional valve is improved compared with the prior art.

This objective is met in that the check valve is arranged in an annular gap surrounding the piston guide sleeve in the area of the pressure medium inlet. Through this construction, on one hand, the check valve is integrated into the actual proportional valve so that the check valve does not have to be installed as a separate component during the installation of the proportional valve. On the other hand, because the check valve is arranged outside of the piston guide sleeve it is guaranteed that the check valve cannot be moved in the radial direction against the valve piston. Incidentally, the proportional valve constructed in this way is preferably used for adjusting the camshaft of an internal combustion engine.

In continuation of the invention, the annular gap is limited by an insert-molded part at least partially surrounding the piston guide sleeve and a receptacle sleeve comprising at least a sub-region of the insert-molded part. Several advantages are achieved with this construction. No additional installation expense is required for the installation of the camshaft adjuster, wherein the risks of installation errors due to an incorrectly installed, an additional check valve or even no check valve at all are minimized. Furthermore, no additionally processed installation space on the cylinder head of the internal combustion engine is necessary for a separate check valve and a hydraulically short distance to the actual camshaft adjuster and thus a stiffer hydraulic support is achieved.

In continuation of the invention, the receptacle sleeve has, on its axial end, a receptacle gap that forms a partial region of the annular gap and in which the check valve is inserted. This construction allows an especially simple and reliable installation of the check valve, in that this check valve is inserted into the end-side receptacle gap without the use of tools and then the piston guide sleeve is inserted into the receptacle sleeve. This construction also reduces the processing costs for the components, in particular, the piston guide sleeve. In contrast to the prior art, in the construction according to the invention the piston guide sleeve is not processed for forming the annular gap.

In another construction of the invention, the piston guide sleeve provided with the insert-molded part is connected to the receptacle sleeve with a material-fit connection. Here, according to an installation method according to the invention, the check valve is inserted in a receptacle gap of the receptacle sleeve forming a partial region of the annular gap and then the piston guide sleeve provided with the insert-molded part is inserted into the receptacle sleeve and connected to this sleeve, for example, with a material-fit connection. Alternatively, a non-positive-fit or positive-fit connection could also be provided. The material-fit connection could be realized, for example, by ultrasonic welding or bonding. A non-positive connection is achieved, for example, by pressing the piston guide sleeve provided with the insert-molded part into the receptacle sleeve, while a positive-fit connection can be realized by a snap connection. All of these constructions have the advantage that they provide an extremely functional proportional valve for a camshaft adjuster.

In continuation of the invention, the check valve is constructed as a spring sleeve with slots in the axial direction, wherein it can be produced, in turn, advantageously from a metallic material, for example, sheet metal or stainless steel.

In another construction, the insert-molded part forms, on its outer lateral surface, a stop acting in the radial direction in the open position of the check valve and the receptacle sleeve forms, on its inner lateral surface, a stop acting in the radial direction in the closing direction of the check valve. In the deactivated state, the check valve contacts the inner lateral surface of the receptacle sleeve with no force or in a slightly pretensioned state. If pressure medium fluid, in particular, hydraulic fluid, flows from the outside in the radial direction into the adjustment space of the proportional valve, then the check valve is pressed by the pressure of the pressure medium fluid against the outer lateral surface of the insert-molded part and opens the inlet. If there are pressure fluctuations against the flow, then the check valve closes against the radial pressure medium inlet of the receptacle sleeve. This construction offers the advantage that a reliable function is guaranteed. In each case it must be guaranteed that a collision of the check valve with the valve piston is excluded.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional advantageous constructions of the invention can be taken from the description of the drawings in which an embodiment of the invention shown in the figures is described in more detail.

Shown are:

FIG. 1 a perspective overall view of the entire proportional valve for the camshaft adjuster,

FIG. 2 a longitudinal section view through the proportional valve with the check valve in a closed position,

FIG. 3 a longitudinal section view through the proportional valve with the check valve in an open position, and

FIG. 4 a cross sectional view through the proportional valve with the check valve in a closed position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The proportional valve 1 according to the invention is provided for a camshaft adjuster of an internal combustion engine. Here, the camshaft driven by the camshaft adjuster is used in an internal combustion engine to open the gas exchange valves used for pushing out combusted gases and for taking in fresh gases against the force of valve springs installed on each gas exchange valve. Fixed control times for the gas exchange valves represent a compromise for the design with respect to the achievable medium pressure maximum or torque maximum and their positions in the usable rotational speed band, as well as the achievable output for the rated rotational speed. An optimal adaptation of the control times of the gas exchange valves can be achieved by a camshaft adjuster according to the respective operating state.

The proportional valve 1 has, according to FIG. 1, an electromagnetic control part 2 whose activation piston 6 interacts with a valve piston 3 (FIGS. 2, 3, 4) in the proportional valve 1. The activation piston 6 of the control part 2 moves the valve piston 3 in a piston guide sleeve 4 of the proportional valve 1 between two end positions and therefore causes a regulated adjustment of the control times on the camshaft adjuster. In addition to the control part 2, the proportional valve 1 also comprises the piston guide sleeve 4 (for a detailed representation, see FIGS. 2 to 4) that is provided in the area of a pressure medium inlet 10 and a working connection 11 b with an insert-molded part 5 made from, in particular, plastic. In the piston guide sleeve 4, the valve piston 3 can be moved by the control part 2 by the activation piston 6 (FIGS. 2 and 3) against the force of a valve spring 7.

The piston guide sleeve 4 provided with the insert-molded part 5 is inserted in a receptacle sleeve 8 and fixed to this sleeve by a snap connection 9 in an exact position on its end facing away from the control part 2 (FIG. 2, 3). The proportional valve 1 has four hydraulic fluid connections, namely a pressure medium inlet 10 connected to a pump, two working connections 11 a, 11 b and a return connection 11 c that is connected to a tank and leads through the interior of the hollow cylindrical valve piston 3.

Through the pressure medium inlet 10, the hydraulic fluid, in particular, the motor oil of the internal combustion engine, is fed to the proportional valve 1 and fed through corresponding passages in the receptacle sleeve 8, the insert-molded part 5, and according to the position of the valve piston 3 via an annular space 12 defined by the control pistons 12 a and 12 b as part of the valve piston 3 to the working connections 11 a, 11 b.

From the working connection 11 a, a connection to the return connection 11 c can be established via a connection opening 16 in the valve piston 3. Ring filters 17 are provided on the pressure medium inlet 10 and also the working connections 11 a, 11 b. These are used to prevent the penetration of dirt into the proportional valve 1.

Through this proportional valve 1 constructed according to the invention, a defined adjustment of the camshaft relative to a drive wheel activated, for example, by a toothed belt or chain is achieved. This is achieved, for example, by one or more adjustment pistons of the camshaft adjuster 1, wherein the piston or pistons is/are connected to the camshaft and rotated relative to the drive wheel by hydraulic fluid introduced through opposing adjustment piston spaces connecting to the working connections 11 a, 11 b.

To prevent a return flow of the motor oil in the annular space 12 back into the hydraulic fluid inlet 10, which could happen due to the changing torque acting on the camshaft and thus on the adjustment pistons of the camshaft adjuster, a check valve 13 is inserted into the hydraulic fluid inlet 10, wherein this check valve contacts the receptacle sleeve 8 in a closed position (FIG. 2) and contacts the insert-molded part 5 in an open position (FIG. 3). Here, the piston guide sleeve 4, the insert-molded part 5, and the receptacle sleeve 8 form an annular gap 14 (FIG. 4) in which the check valve 13 is arranged. To reliably position the check valve 13 (reed valve) constructed as a spring sleeve with axial slots in the annular gap 14, the receptacle sleeve 8 has a tab 15 that interacts with the insert-molded part 5. This tab 15 has the effect that the check valve 13 cannot rotate within the annular gap 14. This prevents incorrect functioning. Furthermore, through the construction according to the invention it is guaranteed that the check valve 13 cannot come into contact with the valve piston 3 in the open position.

LIST OF REFERENCE SYMBOLS

-   1 Proportional valve -   2 Control part -   3 Valve piston -   4 Piston guide sleeve -   5 Insert-molded part -   6 Actuation piston -   7 Valve spring -   8 Receptacle sleeve -   9 Snap connection -   10 Pressure medium inlet -   11 a, 11 b Working connection -   11 c Return connection -   12 Annular space -   12 a, 12 b Control piston -   13 Check valve -   14 Annular gap -   15 Tab -   16 Connection opening -   17 Ring filter 

1. Proportional valve comprising: a piston guide sleeve, a valve piston that can move in the piston guide sleeve, and a check valve arranged in a pressure medium inlet to the proportional valve, the check valve is arranged in an annular gap surrounding the piston guide sleeve in an area of the pressure medium inlet.
 2. Proportional valve according to claim 1, wherein the annular gap is limited by an insert-molded part at least partially surrounding the piston guide sleeve and a receptacle sleeve comprising at least one sub-region of the insert-molded part.
 3. Proportional valve according to claim 2, wherein the receptacle sleeve has, on an axial end thereof, a receptacle gap that forms a sub-region of the annular gap and in which the check valve is inserted.
 4. Proportional valve according to claim 2, wherein the piston guide sleeve provided with the insert-molded part is connected with a material-fit connection to the receptacle sleeve.
 5. Proportional valve according to claim 2, wherein the piston guide sleeve provided with the insert-molded part is connected with a non-positive-fit connection to the receptacle sleeve.
 6. Proportional valve according to claim 1, wherein the check valve is constructed as a spring sleeve with slots in an axial direction.
 7. Proportional valve according to claim 1, wherein the check valve is produced from a metallic material.
 8. Proportional valve according to claim 2, wherein the insert-molded part includes, on a outer lateral surface thereof, a stop that is active in a radial direction in an opening direction of the check valve.
 9. Proportional valve according to claim 2, wherein the receptacle sleeve forms, on an inner lateral surface thereof, a stop that is active in the radial direction in a closing direction of the check valve.
 10. Installation method for a proportional valve with a piston guide sleeve, a valve piston that can move in the piston guide sleeve, and a check valve arranged in a pressure medium inlet to the proportional valve, comprising inserting the check valve into a receptacle gap of the receptacle sleeve forming a sub-region of the annular gap and then inserting the piston guide sleeve provided with the insert-molded part into the receptacle sleeve and connecting the piston guide sleeve to the receptacle sleeve.
 11. Proportional valve according to claim 2, wherein the piston guide sleeve provided with the insert-molded part is connected with a positive-fit connection to the receptacle sleeve. 